Frequency-indicator.



No. 649,007. Patented May 8, |900.

C. P. STEINME'TZ.

' FnEuul-:Ncv INDICATOR.

(Application led Jan. 9, 1899.) (No Model.)

FTB-5.

mnlassas. INVENTDR.

61, Y 'Charles p. Steinmetz ED STATES PATEN Enron.

CHARLEs P. srEINMETZ, OE sCHENECTADY, NEw YORK, AssIeNOR To THE GENERAL ELECTRIC COMPANY, OE NEw YORK.

INDICATOR.

SPECIFICATION forming part of Letters Patent No. 649,007, dated May 8, 1900.

Application led January 9 l 8 9 9.

T all whom, it may concern/ Beit known that I, CHARLES P. STEINMETZ, a citizen of the United States, residing at' Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Frequency-Indicators, (Case No. 642,) of which the following is a specification.

My present invention relates to a method of ro measuring or indicating the frequency of alternating or periodically-varyin g electric cu rrents.

The principle of Operation of my invention depends upon the fact `that the relations eX- isting between the electromotive forces consumed by resistance, inductance, and capacity vary with variation in frequency of the electromotive force impressed. Changes in frequency thus cause changes in the phase zo relations of the system, and I take advantage of this fact by causing'the changes in phase relations to take place between the currents flowing in a plurality of angnlarly-displaced coils within the influence of which is located z 5 a relatively-movable member responsive to the currents in such coils. As the frequency changes the relatively-movable member shifts in position, and thus serves by its changing position to indicate the frequency. `The two forms of apparatus which I have hereinafter described as embodying my invention consist of indicating mechanism each containing relatively fixed and movable mem-y bers,the members being arranged with respect 3 5 to each other so that one member is acted upon by the differential or resultant effect of a plurality of magnetomotive forces produced through the medium of the other member. This mode of action as applied to a frequency 4o indicator I consider to be broadly new.

My invention will be more clearly understood from the following description, taken in connection with the accompanying drawings', in which- Figure l represents one embodiment of my invention; Fig. 2, a different form, and Fig. 3 is a detail.

In Fig. l the relatively-movable member fmJ is arranged to be acted upon by currents traversing two angularly-displaced coils A B.

of the pointer p in opposition to the force of Serial No. 701,597. (No model.)

These coils are arranged iny series with each vThe inductance may be produced by a suitable inductance-coil I, while a condenser C may be used to supply the capacity. The relative values of resistance, inductance, and capacity are so chosen that their effects so far neutralize each other at some predetermined frequency as to render the circuit shunted about the coil A of the same time constant as the coil A itself. Under this' condition currents in the coils A and B are in the samephase with each other, and no effect, therefore, is produced upon the short-circuitcd member m within their influence. The pointer p, carried by the member m, then corresponds to a point on the scale K indicating the frequency of the current then traversing the circuit a b. In this position the restoring-spring S isin its neutral condition and not under tension. If now the frequency in the circuit a b were to rise, the effects of the inductance I and capacity O would no longer bear the same relation to each other, thus causing a displacement of phase of thel current in the coil A and a consequent difference in phase between the currents in the coils A B. The field acting upon the induced member m is therefore no longer reciprocating, but becomes rotary, and thus acts to produce rotation of the induced memberm and consequent movement 8s the spring S. This movement is greater the greater the inequality between the effects of the inductance I and the capacity C, and consequently the greater the change of frequency of current in the circuit ab. y If the frequency were to fall instead of rise, the opposite eifect would take place and the pointer p would move in the reverse direction. By suitable calibration the indications of the pointer may be made to correspond to the values offrequenoy in the circuit to which the indicator is attached. The induced member fmmay consist of a disk or cylinder of conducting materiah as shown, and may operate by reason of the torque due to eddy'currents in-f roo duced therein by the currents circulating in the primary or inducing member, or in place of the disk of conducting material I may substitute a needle or simil-arl elongated piece of magnetic material, as shown separately in Fig. 3. In the latter case no restoring-spring is used; but, on the contrary, the needle is mounted so as to turn freely. The iield which acts on the needle is not of uniform intensity, but varies through a considerable range and, as represented b y polar coordinates, is elliptical in form rather than circular. The eecentrieity of the ellipse, as Well as the posi-` tions of its axes in space, is d ependent upon the phase difference and relative magnitudes of the exciting-currents. So long as the frequency remains constant the axes of the elliptical field do not shift in space, but remain iixed regardless of change in im pressed electromotive force.

I have found that when a needle of magnetic material is mounted, as described, within the influence of an elliptical field it will turn so as. to place itself along the line of greatest magnetization of the iieldin other words, along the major axis of the ellipseand instead of rotating with the field will remain fixed in space and change in polarity as the field reverses in direction. This mode of action presupposes that the needle receives vno initial rotation, and it depends on the fact that the inertia of the needle is such as to prevent it from instantly7 starting into synchronous rotation with the impressed field, the result of which is that the polarity of the needle is continuously reversed, and it is thus alternately subjected to positive and negative torques, which balance each other when the needle is stationary. If the impressed field approaches closely a circular form, the needle will start into rotation of itself; but with the split-phase-inducing members, such as shown in the drawings, the production of such a iield need not occur if proper precautions be taken in designing the apparatus. In any case suitable steps may be provided in order to limit the angle of rotation.

In Fig. 2 I have shown another form of my invention, similar to that of Fig. l, but differing therefrom in important particulars. In this form of indicator two angularly-displaced and relatively-fixed coils A and B' are arranged to be independently excited from the circuit ct b, the frequency of which is to be measured. In series with one of the coils, A', is the non-inductive resistance R, of convenient value, while in series with the other coil, B', is the reactive coil or inductance I', also of convenient value. `Currents passing through the coils A and B will produce a magnetic field due to the resultant action of the magnetomotive forces acting in each coil. Within the iniiuence of this resultant field is located a device of such a nature as to be acted upon dynamically thereby. This device may take the form of a short-circuited secondarywsuch, for instance, as a rotatablymounted disk or cylinder of conducting material--or as an alternative construction it may assume the form of a magnetic needle or similar elongated body of magnetic material, as described above and shown in Fig. 3. Then the relatively-rotatable body consists of a disk or cylinder, it is so mounted as to be capable of movement only through a limited arc, while its movement throughout its range is resisted by some suitable reactive means-as, for example, a spiral spring or the like. If a needle of magnetic material is used, it is mounted so as to turn freely.

In Fig. 2 I have shown a disk or cylinder m, of conducting material, forming the relatively-movable part of the indicator, while the spiral spring S is used to produce the restoring moment for the relatively-movable member. A pointer or hand p is att-ached to the movable member m of the indicator and is arranged to move over a suitably-graduated scale K. In the operation of the indicator current passes through both of the actuatingcoils A and I3' and the pointer p takes a position such that the resultant action of the magnetomotive forces due to current in coils A and B upon the relatively-movable disk or cylinder m within their influence is balanced by the torsional force of the spring S. If new the frequency of the current in the mains ct i) were, for example, to increase, the current through the coil A', containingin series therewith the resistance R, would remain unchanged so long as the electrometive force impressed did not vary. On the other hand, the current through the coil B, having in series therewith the induetance I', no longer remains the same, but would decrease in value and shift in phase with increase of frequency, thus changing the torque due to the resultant field acting upon the relatively-movable member m of the indicator, and so shifting i the pointer p 4to a new position on the scale.

After suitable calibration the scale K may be suitably subdivided in any desired manner.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. The method of indicating the frequency of alternating current which consists in deriving therefrom a plurality of magnetomotive forces, acting by said magnetomotive forces upon a device responsive thereto and rotatable only through a limited arc, and altering the relation of said magnetomotive forces in accordance with the alterations in frequency of said current.

2. The method which consists in acting upon a movable responsive device by a plurality of magnetomotive forces which alter iupon a movable responsive device by two magnetomotive forces which alter their phase relations with changes in frequency of the IOO currents to which they are due, and indicating by the position of such device the frequency of said currents.

4. The method of indicating the frequency of alternating current, which consists in deriving therefrom two -magnetomotive forces which alter their phase relations with changes in frequency of said current, acting by said magnetomotive forces upon a device responsive thereto and indicating by the position of saidv device the frequency of said current.

5. The method of indicating the frequency of alternating current, Which consists in deriving therefrom a plurality of magnetomotive forces the resultant of which changes with changes of frequency of said current irrespective of changes in electromotive force of the current, acting by said resultant magnetomotive force upon a device responsive thereto and indicating by the position of said device the frequency of said current.

6. The method of indicating the frequency of alternating current, which consists inproducing thereby a plurality of phase-displaced magnetomotive forces, combining said magnetomotive forces so as to produce an unsymmetrical rotary field, shifting the major axis of said rotary field in space as the frequency varies, and indicating the frequency by indicating the position of said major axis.

7. The method of indicating the frequency of alternating current, which consists in producing thereby a plurality of phase-displaced magnetomotive forces, combining said magnetomotive forces so as to produce an unsymmetrical rotary field, shifting an axis of said rotary field in space as the frequency varies, and indicating the frequency by indicating the position of said axis.

8. The method which consists in acting upon a movable responsive device by a plurality of magnetomotive forces, changing the relations of said magnetomotive forces With changes in frequency ofthe currents to which they are due, and indicating the frequency of said currents by the position of said device.

9. The method which consists in acting upon a movable responsive device by re1atively-phase-displaced magnetomotive forces, causing a displacement of said responsive device in accordance with variation of frequency of current to Which said magnetom otive forces are due and irrespective of changes of voltage in said current, and indicating the frequency of current by the position of said device.

In Witness whereof I have hereunto set my hand this 5th day of January, 1899.

CHARLES P. STEINMETZ.

Witnesses:

B. BgHULL, M. H. EMERSON. 

